Early last month, Google wrote a seemingly innocuous, jargon-filled blog post about figuring out when a search ad on a consumer's smartphone leads to buying an item in real life—conveniently glossing over the fact that it's doing that by "tracking consumers’ smartphone locations all the time, wherever they go, even when they’re not using a Google app," reports Digiday.

Google may not have made it clear to consumers, but the company has already begun pitching the capability to advertisers, says Digiday:

Google is beta-testing a program that uses smartphone location data to determine when consumers visit stores, according to agency executives briefed on the program by Google employees. Google then connects these store visits to Google searches conducted on smartphones in an attempt to prove that its mobile ads do, in fact, work.

In order for Google to figure out when consumers visit a store, smartphone users have to opt in to location services. But Dan Auerbach from the Electronic Frontier Foundation says they might not realize that means their location is constantly being monitored:

“The disclosure mechanism for these apps are pretty weak,” he said. “I think there’s a gap between user expectations and what apps are really doing.”

The easiest way for Google to do this kind of tracking is on Android phones, " since Google has embedded location tracking into the software." But iPhone users can also be tracked through Google apps:

Google’s namesake iOS app — commonly referred to as Google mobile search — continues collecting a user’s location information when it runs in the background. This information is then used to determine if that user visited a store and whether that store visit can be attributed to a search conducted in the app. Store visits can also be tracked via Google’s other iOS apps that use location services. If iOS users open their Chrome, Gmail or Google Maps app in a store, their location can be deemed a store visit.

For all of those apps, location sharing is "opt-in," so just remember, you did this to yourself.